1. Field of the Invention
This invention relates generally to UV and visible laser systems, and their methods of use, and more particularly to UV and visible laser systems that are suitable for semiconductor inspection or processing.
2. Description of Related Art
An increasing number of laser applications in the semiconductor industry require UV or visible laser light. These applications include inspection as well as materials processing tasks. Many of these applications require that the sample under test be kept clean or be in close proximity to processing equipment, and thus the entire machine is located in a clean room environment.
Diode-pumped solid-state lasers are finding increasing acceptance in this market because of their robustness. These systems consist of several subsystems: a power supply to run the pump diodes, the pump diodes themselves, the laser head, and a harmonic conversion device to generate the visible or UV radiation. Typically, the entire laser system is included within the semiconductor-processing machine, which is located in the clean room.
Diodes used as the pump source can be positioned in the power supply. Pump light is then coupled from the diodes in a multi-mode fiber, and is conveyed to the laser head by an armored fiber cable. In this way, the power supply and diodes can be located remotely, while the laser head and harmonic conversion device are located in the semiconductor-processing machine. The power supply and diodes can be outside the machine or even outside the clean room.
However, positioning the diodes in the power supply, followed by coupling the diode pump light in a multimode fiber, works because the pump light is: in the IR, continuous wave, and not diffraction limited. In contrast, the output of the laser is visible or UV, is often pulsed, and has a diffraction limited beam. Thus, single mode fibers are required to preserve the beam quality, but are problematic with both pulses and UV radiation.
There is a need for improved UV and visible laser systems that are suitable for semiconductor inspection or processing. There is a further need for UV and visible laser systems for semiconductor inspection or processing applications where the laser resonator and power supply are positioned at a location external to a clean room.
Accordingly, an object of the present invention is to provide diode-pumped lasers, and their methods of use, in remote location applications.
Another object of the present invention is to provide diode-pumped lasers, and their methods of use, in semiconductor inspection or processing applications with the laser resonator and power supply positioned at a location external to a clean room.
These and other objects of the present invention are achieved in a laser apparatus that includes a modelocked laser system with a high reflector and an output coupler that define an oscillator cavity. An output beam is produced from the oscillator cavity. A gain medium and a modelocking device are positioned in the oscillator cavity. A diode pump source produces a pump beam that is incident on the gain medium. A second harmonic generator is coupled to the oscillator cavity. A third harmonic generator that produces a UV output beam, is coupled to the second harmonic generator. A photonic crystal fiber is provided with a proximal end coupled to the laser system. A delivery device is coupled to a distal portion of the photonic crystal fiber.
In another embodiment of the present invention, a laser apparatus includes a modelocked laser system with a high reflector and an output coupler that define an oscillator cavity and produces an output beam. A gain medium and a modelocking device are positioned in the oscillator cavity. A diode pump source produces a pump beam that is incident on the gain medium. A first amplifier is also included. A second harmonic generator is coupled to the first amplifier. A third harmonic generator that produces a UV output beam, is coupled to the second harmonic generator. A photonic crystal fiber is provided with a proximal end coupled to the laser system. A delivery device is coupled to a distal portion of the photonic crystal fiber.
In another embodiment of the present invention, a laser apparatus includes a modelocked IR laser system with a high reflector and an output coupler that define an oscillator cavity. A gain medium and a modelocking device are positioned in the oscillator cavity. A diode pump source produces a pump beam that is incident on the gain medium. A photonic crystal fiber is provided with a proximal end coupled to the IR laser system. A harmonic conversion delivery device is coupled to a distal end of the photonic crystal fiber.
In another embodiment of the present invention, a laser apparatus includes a modelocked IR laser system with a high reflector and an output coupler that define an oscillator cavity. A gain medium and a modelocking device are positioned in the oscillator cavity. A diode pump source produces a pump beam incident on the gain medium. A first amplifier is also included. A photonic crystal fiber has a proximal end coupled to the IR laser system. A harmonic conversion delivery device is coupled to a distal end of the photonic crystal fiber.
In another embodiment of the present invention, a method of delivering a UV output beam to a remote location provides a modelocked infrared laser system. The laser system includes a high reflector and an output coupler that define an oscillator cavity that produces an output beam. A gain medium and a modelocking device are positioned in the oscillator cavity. A photonic crystal fiber is provided and has a proximal portion coupled to the laser system, and a distal portion coupled to a delivery device. The infrared laser system is positioned at a distance from the remote location. A UV output beam is produced at a distance from the remote location. The UV output beam is delivered to the delivery device at the remote location.
In another embodiment of the present invention, a method of delivering an UV output beam to a remote location is provided. A modelocked IR laser system includes a high reflector and an output coupler that define an oscillator cavity that produces an output beam. A gain medium and a modelocking device are positioned in the oscillator cavity. A diode pump source produces a pump beam that is incident on the gain medium. A harmonic conversion delivery device is positioned at the remote location. A photonic crystal fiber is provided that has a proximal portion coupled to the IR laser system, and a distal portion coupled to the harmonic conversion delivery device. The IR laser beam is delivered with the photonic crystal fiber from the IR laser system to the harmonic conversion delivery device. A UV beam is produced from the harmonic conversion delivery device at the remote location.